The present invention relates to a method of commissioning an internal combustion engine controlled by an electronic engine control unit and relates particularly, but not exclusively, to an engine mapping function incorporated in the method of commissioning.
Co-pending application Ser. No. 09/269,791 filed Apr. 1, 1999 describes an improved engine control unit (ECU) for controlling the operation of a gas fuelled internal combustion engine. The disclosure of Ser. No. 09/269,791 is incorporated herein by reference.
The ECU uses various engine operating parameters stored in non-volatile memory to control the operation of the engine. These parameters may be programmed through a serial port by an external device. The engine operating parameters are collectively known as the engine control set (ECS). The ECS includes numerous parameters defined and stored in table form, including the Engine Speed Table, Startup Spark Advance Angle Table, Startup Injector On Time Table, Water Jacket Temperature Throttle Limit Table, Manifold Air Temperature Throttle Limit Table, Exhaust Temperature Throttle Limit Table, Individual Injector Switch On Time Table, Individual Injector Flow Rate Table and the MVP Area Table, most of which are self-explanatory. These parameters are stored in the ECU memory during commissioning of the ECU following engine mapping.
As part of the process of commissioning an engine, it is mapped at a combination of speeds and loads to build up the full ECS that gives the engine its required performance. This covers steady state torque output, maximum speed governing and emissions, whilst observing the original equipment manufacturer""s (OEM""s) limits on thermal loads and maximum cylinder pressure. During this process the ECU automatically compensates for gas pressure and temperature variations that inevitably occur such that the injector on-time (IOT) to be recorded is referenced to standard gas pressure and temperature. Similarly, ignition timing is modified according to the manifold air temperature such that the recorded values are augmented if the air temperature is higher than the set reference temperature of 25xc2x0 C. and conversely if the air temperature is lower than the reference. When mapping is finished all engine operating parameters are downloaded into the ECU.
The present invention was developed with a view to providing a method of commissioning an ECU and performing various executive functions such as engine mapping.
According to the present invention there is provided a method of commissioning an internal combustion engine controlled by an electronic engine control unit, the method comprising:
mapping a selected engine operating parameter over a range of engine speeds and loads so as to obtain optimum values for said selected engine operating parameter for different speeds/load combinations, said mapping process involving the steps of:
(a) defining a speed/load mapping table and generating a graphical display of a corresponding speed/load grid comprising a plurality of cells arranged in a grid, each cell corresponding to a particular speed/load combination in the speed/load mapping table, each unmapped cell in the grid being displayed in a first visually distinct manner and each mapped cell being displayed in a second visually distinct manner;
(b) selecting an unmapped cell in said speed/load grid for mapping;
(c) driving the engine as close as possible to the selected speed/load combination;
(d) displaying the current value of said selected engine operating parameter;
(e) adjusting the value of said selected engine operating parameter to thereby obtain an optimum value for said engine operating parameter at said selected speed/load combination;
(f) saving the optimum value at said selected speed/load combination in the speed/load mapping table; and,
(g) repeating steps (b) to (f) until the selected engine operating parameter has been mapped for all desired cells in the speed/load grid.
Preferably one cell in the speed/load grid is displayed in a third visually distinct manner to indicate the engine""s current operating position. Preferably said step of selecting an unmapped cell for mapping (step (b)) includes displaying said selected unmapped cell in a fourth visually distinct manner.
Advantageously said selected engine operating parameter is one of a plurality of selected engine operating parameters which may be mapped simultaneously using the speed/load grid. In a preferred embodiment said plurality of selected engine operating parameters are manifold valve position (MVP), injector on time (IOT) and spark advance angle (SAA). Step (c) in the method may be performed by controlling the engine throttle and/or by manipulating the values for MVP, IOT and/or SAA, and/or setting the dynamometer speed.
Advantageously the graphical display of said speed/load grid is displayed as part of an engine mapping dialog box, said engine mapping dialog box including a read-only display of the current value of said selected engine operating parameter, a scroll bar for changing an offset value of said selected engine operating parameter and a read-only display of the resulting value of said engine operating parameter which is the sum of the current value and the offset value, wherein step (e), adjusting the value of said selected operating parameter, involves scrolling to an appropriate offset value using said scroll bar to obtain the optimum resulting value for said selected engine operating parameter.
Preferably said engine mapping dialog box also includes a plurality of IOT offset spin boxes, one for each of the engine""s injectors, and wherein the method of commissioning further comprises applying an individual IOT offset to a base IOT offset for any one or more of the injectors.
Advantageously the method of commissioning may optionally provide for automatic balancing of exhaust temperatures for each cylinder of the engine, wherein said step of automatically balancing involves:
logging exhaust temperatures for each cylinder of the engine;
averaging the exhaust temperature values across all cylinders to obtain an average exhaust temperature value;
calculating a deviation of the exhaust temperature value for each cylinder from said average exhaust temperature value; and,
adjusting the individual IOT offsets for each injector simultaneously based on said respective deviations whereby, in use, the exhaust temperatures for each cylinder can be brought closer to the average exhaust temperature value.